Process of flotation separation of ore



Patented Oct. 135, 1942 PROCESS or FLOTATION SEPARATION or one Hoyt M. Corley, Anderson W. Ralston, and Ervin W. Segehrecht, Chicago, Ill., assignors to Armour and Company, Chicago, 111., a corporation of Illinois No Drawing. Application October 11, 1939,

Serial N- 299034 14 Claims. (01. 209-466) This invention relates to ore separation agents comprising admixtures of primary aliphatic. amines having at least six carbon atoms with straight chain aliphatic nitriles having at least six carbon atoms, both'of such substances bein in substantial quantities, it further comprises processes wherein ores are subjected to a froth flotation in the presence of a mixture of primary aliphatic amines containing at least six carbon atoms andaliphatic nitriles containing at least six carbon atoms, and it more specifically comprises processes wherein siliceous minerals are separated from non-siliceous minerals by 110- tation in the presence of straight chain aliphatic nitriles and primary aliphatic amines, both of.

which contain at leastsix carbon atoms.

The higher primary aliphatic amines are important flotation agents because they show a high degree of selectivity for certain constitu- 7 more costly than the fatty acids themselves. can be said categorically that the relatively high extentjthe' primary aliphatic amine salts," are 4 highly effective for theseparation of silica. They tailing.

It has been shown experimentally that the higher primary aliphatic amines, and by that term in the present specification we mean to include those amines having at least six carbon atoms, and exclude those having a lesser number of carbon atoms, function quite differently from the higher primary aliphatic amine salts. The amine salts, as has been recognized by prior workers in this art, will ionize in water to form so-called cation-active surface agents. These surface-active agents act selectively upon certain constituents in the ore and are analogous to the so-called surface-active wetting agents, all of which depends upon ionization for their functioning. On the other hand, the primary aliand do not undergo ionisation. This holds true for all higher members of the series, namely those having twelve or more carbon atoms. 'It is an observed fact, however, that the higher pri mary amines do function differently from the corresponding amine salts. Undoubtedly, the primary amine is adsorbed by certain ore values as a kind of surface layer one or two moleclues thick. Experimental results show quite wide differences between the behavior of primary amines and primary amine salts. This is especially noticeable when comparisons are made between the amounts of these two agents which are necessary to give equal results. The flotation can be successfully practised with less primary amine per ton of ore than is required when primary amine salts are used. Moreover, the selective index for the separation is greater when primary amines are used.

However, those primary amines and their salts which have flotation properties are relatively expensive substances. Since they are prepared from the corresponding fatty acidsthey ar thus It cost of the primary amines has, and probably will in thefuture, prevent the use of the primary "amines alone as flotation agents; This is'so in constitute an important step forward in this art.

Accordingly, we have set ourselves to the problem of discovering-ways by which higher pri mary amines can be used for the flotation separation of ores under such conditions that the cost per ton of ore is greatly lessened; And as a result of our experiments we have discovered that the amount of such primary amines ordinarily required to perform some particular separation can be greatly reduced provided substantial quantities of higher primary aliphatic nitriles are used in admixture with the primary amine.

Thus, for example, such an aminenitrile mixture will contain approximately to 80% by weight of primary aliphatic amines having six or more carbon atoms and 50% 'to 20% by weight of primary aliphatic nitriles having at least six carbon atoms,

But the use of nitriles in conjunction with the amines is not simply one of diluting the amount of amine by the addition of nitriles thereto.

phatic amines themselves are insoluble in water Indeed the nitriles themselves are relatively ex- 'pensive materials since they must also be made For example, some separations may require as much as six pounds per ton of a primary aliphatic amine having at least .six carbon atoms. An even better separation of such an ore can be obtained when only one pound of a mixture of nitriles and amines is used. In every instance the amount of amine-nitrile mixture is always far less than the amount of primary amine which would be required if that substance were used alone. We emphasize this so that it will be clearly understood that we are not'merely substituting a quantity of nitriles for a part of the primary amine ordinarily required for performing the separation when used alone.

Thus, in broad aspects, thepresent invention comprises as a new flotation agent a. mixture of primary aliphatic amines and aliphatic nitriles, each of which contains at least six carbon atoms and in which both substances are present in substantial quantities. The pending application of Ralston et al., Serial No. 116,422, discloses mixtures or amines and nitriles but the quantities of nitrile therein is not more than about 4% or 5% and are simply small amounts of nitriles which have not been reduced to amines. The present invention differs from that co-pending application in that the amount of nitriles is substantial, never less than about and it is only when substantial quantities ofnitriles are present that the particular function of the nitriles in reducing the amount of amines necessary comes into play.

In more specific aspec'tslour invention embraces theflotation separation of ores by using the nitrile-amine mixtures of the present invention, and in still more specific aspects the present invention includes processes wherein silica is separated fromv non-siliceous minerals by means of artmay understand the technical advantages rethe nitrile-amine mixtures of the present invention.

As stated, the amines which we use are all-pri-j mary aliphatic amines containing at'leastsix carbon atoms. These range from hexylamine,

up to octadecylamine having eighteen "carbon atoms. The amines may be either saturated or unsaturated, or mixtures of both. They are 'most conveniently prepared by converting ratty acids, such as cottonseed oil fatty acids, to the corresponding nitriles, and then reducing those nitriles to the corresponding amine. In such instances, the amines obtained will be a mixture of saturated and unsaturated amines in which the alkyl group is predominantly octadecyl or octadecenyl, together with minor quantities of should be at least about 20% of nitriles in the mixture used as a flotation agent. Generally the amount of nitriles present does not exceed about 50%, but the operable range is from about 20% to about the rest being primary amines. The nitriles are soluble in the primary aliphatic amines, and, consequently, we prepare solutions of the nitriles in the amines and add these mixtures to the ore pulp to be separated. The flotation process itself differs in no way from that hitherto practised in the art.

In the foregoing we have generally emphasized admixtures of primary amines and aliphatic nitriles as the flotation agent in our process. We do not wish to exclude flotation in the presence of amine salts and the nitriles. But when amine salts are used it is best to add a mixture of primary amines and nitriles to the ore pulp and then acidity the .pulp to such a point where the primary amines are converted to their corresponding salts. The nitriles are not soluble in primary amine salts, but it is possible, as an alternative method, to add the nitriles and the amine salts separately to the ore pulp to be treated. Since we have discovered that the amines function better than the amine salts in conjunction with substantial quantities of nitriles we prefer to use the amines in free base form rather than the amines as amine salts. But we do 'not wish the present invention to be so narrowly construed as to exclude flotation under such conditions that the added amines can be considered to exist as amine salts, or where the amine is directly added to the pulp in the form of its corresponding salt. Such salts are watersoluble and are hydrochlorides or acetates in most cases. But we also wish to emphasize that the amines are not the equivalents of the amine salts as will be pointed out in examples which we shall give presently.

We shall now describe a number of examples illustrating results which we have obtained on various types of ores so that those skilled in the siding in our process.

Example 1 36.459 grams of a 'deslimed phosphate ore which analyzed 15.25% P205, 20.96% CaO and 60.25% 5102 were placed in a Denver type flotation cell and 0.28 lb. per ton of a nitrile-amine mixture added. The mixture consisted of 64% amines prepared from palm oil nitriles and 36% nitriles prepared from cottonseed oil acids. Before the addition of the reagent the pH of the slurry was adjusted to 9.5 by the addition of sodium hydroxide solution. The flotation resulted in a concentrate which weighed 20.951 grams and a tailing which weighed 15.508 grams. The composition of the concentrate was as follows: SiOz, 89.87%, CaO, 5.14%, and P205, 2.95%. The composition of the tailing was as follows: SiOz, 15.07%, CaO, 44.25%, and P205, 32.42%. The percent B. P. L. of the tailing is, therefore, 70.8 and the percent recovery of the phosphate 89.05.

For comparison a similar sample was separated using octadecyl amine alone as the flotation agent. The sample required three pounds per ton of the amine and the phosphate recovery was 74.6%.

Thus from the above example it is apparent that only 0.28 pound per ton of the nitrile-amine mixture was necessary to get a percentage recovery of 89.05 whereas three pounds per ton of octadecyL the same number of carbon atoms.

present in admixture with primary amines the total amount of'nitrile-amine mixture is far less than "the"; amount of octadecylamine required when this substance is used alone.

We shall nowgive an example wherein the amine is converted to an amine salt, namely the acetate; bythe addition of. acetic acid prior to performing the flotation.

. Ewample 2 38.691 grams of the ore described in Example 1 were treated with 0.28 pound per ton of a nitriIe-amineQmixture. The mixture consisted of 66 of 'amines prepared by the hydrogenation of palmfoil nitriles and 34% of nitriles prepared from cottonseed oil fatty acids. The flotation was conducted in the Denver type flotation cell which was men'tioned under Example '1. The pH of the slurry was adjusted to 5.4 by the addition of acetic acid. This adjustment in pH was made that at-least four pounds per ton of reagent was required to produce a satisfactory separation when amines such as dodecylamine or octadecylamine were employed. For example, in a typical run, four pounds per ton of octadecylamine gave a product which analyzed 71.2 percent B. P. L. The phosphate recovery in this instance was 68.89%.

A sample weighing 29.662 grams was floated with the equivalent of 2.2 pounds per ton of an amine-nitrile mixture. The mixture used consisted of 33% octadecylamine and 67% octadecyl nitrile. The concentrate weighed 11.370 grams and had the following percentage composition:

and analyzed as follows:

after the nitrile-amine mixture had been added.

The flotation resulted in a concentrate which weighed 28.120'grams and analyzed as follows: SiOz, 71.13%, CaO, 38.95%, and P205, 28.75%. Under these conditions the phosphate recovery A comparison of this example with Example 1 shows that while the flotation using nitrile-amine mixturesconducted on the acid side are satisfactory as far as the amountof material floated is concerned, the, selectivity is not as great as when the flotation is conducted on the alkaline side. In fiotationsconducted on the acid side the amine is present as an amine salt as distinguished from the undissociated amine which is present when the notations are conducted on the alkaline side.

Examples 1 and 2 describe results obtained Si0z, 30.40%, R203, 3.86%, CaO, 29.50%. and P205, 22.35%. The tailings weighed 18.292 grams S102, 6.30%, R203, 4.02%, 02.0, 44.70%, and P205, 33.21%. The percent B. P. L. of the tailings is, therefore, 72.55

and the phosphate recovery 70.51%.

In Example 4 the amount of amine-nitrile mixture required is rather high, namely 2.2 pounds per ton of ore. This large amount in comparison with Example 3, is due to the very fine state of sub-division of the ore. We have found that when the ore is very finely divided somewhat larger quantities of flotation agents are neces sary. regardless of the character of the flotation agent. Yet the example shows that only 2.2 pounds per ton of amine-nitrile is necessary to get an even higher recovery than can be obtained when primary amines, or amine salts having sixteen and eighteen carbon atoms are used. Ex ample 3, which follows, shows results obtained when the primary amine contains sixteen carbon 'atoms and the nitrile contains eighteen carbon atoms. It may be stated at this point that it is not necessar that the nitrile and amine have These can vary from six to eighteen.

Example 3 flotation cell with 0.56 lb. per ton of a mixture which consisted of 75% of hexadecyl amine and 25% of octadecyl nitrile. The sample weighed 37.440 grams.

The concentrate weighed 9.983 grams and had the following composition: S102, 96.66%, CaO, 1.99%, and P205, 1.35%. A further addition of reagent (0.28 lb. per ton) was made which resulted in a concentrate which weighed 10.819 grams and had the following composition: SiOz, 81.18%, CaO, 9.72%, and P205, 7.16%. The tailing weighed 16.638 grams and analyzed as follows: S102, 19.92%, CaO, 41.46%, and P205, 31.06%. This corresponds to a phosphate recovery of 85.03%.

Example 4 when four pounds per ton of octadecylamine alone is used.

Example 5 l A deslimed sample of the same ore was floated with the equivalent of 1.6 lbs. per ton of a mix-' ture which consisted of 33% nitriles prepared from coconut fatty acids and 67% amines pre-' A deslimed sample of the same ore was treated with the equivalent of 1.1 lbs. per ton of a mixture whichconsisted of 33% palm oil amines and 67% of nitriles prepared from cottonseed acids. This flotation gave a concentrate which weighed 5.839 grams and had the following composition: SiOz, 41.90%, R203, 3.66%, CaO, 25.60%, and P205, 18.35%. A further amount of reagent corresponding to 0.55 lb. per ton was then added and the flotation continued. This resulted ina concentrate which weighed 6.529 grams andhad the following composition: SLOz, 18.30%, R203. 4.30%, CaO, 36.62%, and P205, 27.42%. The tailings weighed 18.500 grams and analyzed as follows: S102, 5.35%, R203, 3.77%, CaO, 44.35%, and P205, 32.98%. The distribution of the bone phosphate of lime, is, therefore, as follows: 72.01% in the tailings, 10.48% in the first concentrate and 17.51% in the second concentrate. The percent B. P. L, of the tailings was 72.03. The percentage distribution of the silica was as follows: 21.38% in the tailings, 55.21% in the first concentrate, and 23.41% in the second concentrate.

SiOa. I

Example 7 49.567 grams of a fluorspar ore which analyzed 73.5% calcium fluoride and 21.6% silica was treated in the flotation cell with 0.25 lb. per ton of a nitrile-amine mixture. tained 60% octadecylamine and 40% lauronitrile. The'concentrate weighed 29.736 grams and contained 94.8% calcium fluoride and 4.5% silica. The tailings weighed 19.831 grams and contained 42.39% silica and 41.92% calcium fluoride. This corresponds to a recovery of 77.14% of the calcium fluoride in the concentrate and a rejection of 87.48% of the silica present.

For purposes of comparison a sample of the same ore was separated by the use of octadecylamine. sample required two pounds of amine per ton of ore. This resulted in a separation of 75.78% the calcium fluoride as a concentrate and a rejection of 85.72% of the silica in the tailing.

Example 8 A sample of calcite which contained 91.18% of calcium carbonate and 7.32% silica was placed in the flotation cell in the equivalent of 0.15 pound per ton of a mixture of dodecylamine and hexadecylnitrile. The mixture contained 50% by weight of dodecylamine. The original sample weighed 50.124 grams. Separation resulted in a concentrate which weighed 4.388 grams and which contained 31.18% silica. The tailings weighed 45.736 grams and analyzed 95.41% calcium carbonate and 3.72% silica. This corresponds to a separation of 95.48% of the calcium carbonate in the tailings and 53.41% of the silica in the concentrate. V i g A similar sample required 0.60 pound per ton of dodecylamine to obtain a comparable result.

The foregoing example illustrates the efiectiveness of our amine-nitrile mixtures with a number of non-metalliferous ores from which it is desired to separate the silica. Good results are also obtained when the amine-nitrile mixtures of the present invention are used'for the separation of constituents of metalliferous ores, such as the various copper sulfide ores. Examples 1 and -2 also illustrate the wide diiference in behavior between the amines and the amine salts.

Results are'very much better when flotation in the presence of the free amines is insured by maintaining the slurry on the alkaline side. But for the sake of showing the scope of our invention we have included an example illustrative of results obtained when operating on the acid side.

Having thus described our invention, what we claim is: I

1. The process of separating ores which comprises subjecting the ore to flotation separation in the presence of a flotation agent comprising a mixture of at least one primary aliphatic amine and at least one aliphatic nitrile, each containing at least six carbon atoms, the amount of nitrile being about to about 65% of the combined quantity of amine and nitrile.

2. The process of separating siliceous gangue from ores containing the same which comprises subjecting the ore to flotation separation in the presence of a flotation agent comprising a mixture of at least one primary aliphatic amine and The mixture con- In the Denver type flotation cell the iii) at least one aliphatic nitrile, each containing at least six carbon atoms, the amount of nitrile being about 20% to about 65% of the combined quantity of amine and nitrile.

3. The process of separating silicequs gangue., from phosphate ores containing thesamel'whicn h comprises subjecting the ore to flotati onfsepa ration in the presence of-a flotationagent co prising a mixture of at least one primary, aliph combined quantity of amine and nitrile.

4. The process of separating ores which com prises subjecting'the ore to flotation separation in the presence of a flotation agentcomprising a mixture of at least one primary aliphatic amino compound chosen from the group consisting of primary aliphatic amines having at least six carbon atoms and water-soluble salts thereof, and at least one aliphatic nitrile containing at least six carbon atoms, the amount of nitrile being about 20% to about 65% of the combined'quan'tity of amino P und and nitrile.

5. The process of' separating-phosphatejores: 1

which comprises subjecting the ore to flotation separation in thepresence of a flotation agent comprising a mixture of at least one primary all phatic aminocompound chosen from the group consisting of primary aliphatic amines havingat.

least six carbon atoms and water-soluble salts thereof, and at least one aliphatic nitrile containing at least six carbon atoms, the amount of nitrile being about 20% to about 65% of the combined quantity of amino compound and nitrilefifThe process of separating ores which comprises subjecting an aqueous alkaline slurry of the ore to flotation separation in the presence of a flotation agent comprising a mixture of at least one primary aliphatic amine and at least one aliphatic nitrile, each containing at least six carbon atoms, the amount of nitrile being about 20% to about 65% of the combined quantity of amine and nitrile.

7. The process of separating phosphate ores which comprises subjecting the ore to flotation phatic amine and at least one aliphatic nitrile,

each containing at least six carbon atoms, the amount of nitrile being about 20% to about 65% of the combined quantity of amine and nitrile.

8. The process as in claim 1 wherein the amine and nitrile contain sixteen to eighteen carbon atoms.

9. The process as in claim 2 wherein the amine and .nitrile contain sixteen to eighteen carbon atoms.

10. The process as in claim 3 wherein the amine and nitrile contain sixteen to eighteen carbon atoms.

11. The process as in claim 4 wherein the amine and nitrile contain sixteen to eighteen carbon atoms.

12. The process as in claim 5 wherein the amine and nitrile contain sixteen to eighteen carbon atoms.

13. The process as in claim 6 wherein the amine and nitrile contain sixteen to eighteen carbon atoms.

14. The process as in claim 7 wherein the amine and nitrile contain sixteen to eighteen carbon atoms.

HOYT M. CORLEY. ANDERSON W. RALSTON. ERVIN W. SEGEBRECHT. 

